JLB

I was just curious to see what range of timing values most people are running along with the porting configuration. I have searched for this topic but turned up very little in the form of actual advance numbers - most just advance thiers a little over stock.



I am currently tuning a streetported 6 port that is running on an SDS (fuel only) EFI system. I am using a VDI intake and a free flowing exhaust. Ring now I have an early 80's electronic distributor installed which is triggering the stock S5 leading coil. I am not running any trailing ignition at this time.



I have not yet degreed out my crank pulley, but based on the stock marks I'd say I'm running around 20 degrees total advance. I'm thinking about ditching the distributor and installing a CAS that I highly modified. It has a trigger wheel out of a distributor with 4 teeth on it so it gives two pulses per eccentric revolution. It is much smaller that the distributor (ever try to get to the lockdown nut on a distributor installed on a 2nd gen engine with the PS and AC bracketry in place???) and I would not have to worry about the advance being sloppy...



So, anybody know exactly what full timing they are running at full advance? Ito - any starting suggestions?



Thanks,

Jason

Judge Ito

I would advice for you to get trailing working in your engine. I would suggest that you run your trailing and leading timing with a small split. Mazda Factory Racing recommends running a 20 BTDC for Leading and 20BTDC for trailing for max N/A power.



I personally don't like to take a risk and run no split with my ignition timing. I try to be on the safe side and run a 5 degree split between lead and trail. You could start running 28 degrees before top dead center for leading and 23 degrees BTDC for trailing and see how that feels.

I have found that running leading and trailing with very little split allows an N/A engine to make respectable power. A 12-A distributor has a 15 degree split thats set by Mazda from factory specs. Your going to have to internally(inside the dizzy) turn the screws that hold the trailing pick up coil loose and advance the pick up coil to get the desired smaller split..ONLY DO THIS if the dizzy will not allow you to get a 5 degree split when pulling the advance timing canister on the side of the dizzy. On some dizzy's I couldn't get a 5 degree split between lead and trail when the dizzy was at full timing advance by pulling on the trailing canister for timing advance. When this is the case, you need to manually advance the trailing pick up coil inside the dizzy and re-check with your timing light.

I hope this helps a little.

Jeff20B

I can visualize what you're saying.

JLB

Ok, thanks for the input. I was planning on getting the trailing going too, just hadn't made it that far yet.



A couple more questions for you Ito:



What do you think of ditching the advance in the distributor? Just running the full advance at all RPM's?



It seems like I remember there being a port timing reason for not waste-firing the trailing. Is that correct? If it isn't a problem I could go with an ignition box that has a constant retard setting and dial in the trailing that way - and use another 2nd gen leading coilpack... I would just like to get rid of the that giant distributor and cap!



Thanks,

Jason

j9fd3s

i looked at the timing of the gsl-se and the 20b cosmo (we have a secret book ) and they both run a 10degree split up top, stock. so does paul yaw. so 10degree split at wot is a good starting point.



on the its car we ran 22 degrees btdc advancing to 26 after peak power, it made for a really broad peak, start at like 20 and go from there, depending on the fuel quality etc you might find some detonation over 20-22.



ive noticed at the lower speeds (under 2k) if its over advanced the engine will pop, or misfire more, this isnt really a problem (unless you wanna pass smog) more of an observation.



oh and ito we chaecked what the 12a does during decel and we were surprised

JLB

Ok, cool - thanks for the info. I did forget to mention that I'm running S5 rotors - so it's got a pretty high compression ratio....

j9fd3s

we are too, on 91 gas. we have to be careful it doesnt ping, you might not.

Judge Ito

If this is a street car your running this set up in. I would not like to eliminate the centrifugal timing advance. When your running a locked or full advanced timing in a street car you loose low rpm power.



You cannot run a wasted spark for your trailing coils, only for leading.

The best way to play around with ignition timing is in a dyno one run at a time. Still you have a base timing that you could start here with the help you've been giving so far.

JLB

Yes, it is a street car. Well, I just finished with a little tweaking. First, I pulled the crank pulley off and laid out timing marks in 5 degree increments from TDC to 25 BTDC. I used a very small file to make notches at each mark, then used and engraving tool to label a couple of them. Makes it very easy to see right where you are. And, it turned out that at full advance I was way more advanced than I thought.



So, I set the leading for 20 degrees at full advance. I then connected the trailing ignition with a stock 1st gen coil so that the trailing was going through the cap and rotor. The leading is still just getting a signal from the pickup in the dist to waste fire the 2nd gen coil. I set the trailing at 10 degrees full advance.



I can't let a little thing like freezing rain interfere with my tuning so I just took it for a spin (but not literally!). I was actually impressed with how it ran! Granted, the timing might not be perfect, but now it's finally close enough that I can focus more on fuel mapping. Before it was just too many variables to guess at all at once. Over the weekend I took off the stock S5 NA fuel injection and installed my now 10 year old SDS EFI. For those that say this is not a good system I challenge you to find a unit as reliable that comes with anywhere near the customer service this unit does - specially for the price. But anyway, I cannot begin to estimate the performance gain I'm already seeing over the stock injection and it's not even dialed in yet! After building the street ported engine the stock injection ran way too RICH to run very well - and the stock air flow meter was probably choking things down, too. I found totally disconnecting the boost sensor (which defaults to the lean side) actually made it run better! I never expected it to go rich like that, but since then I have found many people on here that also had that happen.



I am thinking about a dyno adventure in the near future to dial everything in. But first I want to get it running as good as possible by just driving it. There are several chassis dynos near me - the closest is actually an eddy current one that allows a steady speed loading as well as the conventional pulls...



Thanks for all the input everyone!



Jason

Judge Ito

good look..